EP0031194A1

EP0031194A1 - Method and apparatus for forming a tyre sidewall protector

Info

Publication number: EP0031194A1
Application number: EP80303372A
Authority: EP
Inventors: Richard W. Kizer; Arlynn W. Anderson; Robert W. Unty
Original assignee: Caterpillar Tractor Co
Current assignee: Caterpillar Inc
Priority date: 1979-12-17
Filing date: 1980-09-25
Publication date: 1981-07-01
Also published as: CA1118973A; EP0031194B1; JPS56501755A; WO1981001680A1

Abstract

Apparatus for use in a method of forming the mounting portion of a tyre sidewall protector includes a mould (19) in which a sidewall protector (12) can be formed and a separate plate assembly (29,31) which is moveable towards the mould to form the mounting holes (10), central opening (11) and a pair of annular ribs (14,16) on opposite sides of the sidewall protector. Movement of the plate (32) is carried out by a plurality of springs (47) each positioned between the plate (32) and an enlarged head portion (48) of a pin (46). The springs are compressed by a linear actuator (43) and the pin (46) is connected to the mould (19) by a dowel (54) inserted through a hole (53) in the pin (46) to maintain the compression on the springs (47). This apparatus permits the use of automated strip applying equipment for laying up the sidewall protector within the mould (19) while the plate assembly (29, 31 ) accurately forms the mounting portion which includes the mounting holes (10), annular opening (11), and the annular ribs (14,16).

Description

The invention relates to an apparatus for use in and method of forming the mounting portion of an elastomeric article, particularly a tyre sidewall protector.
Sidewall protectors are used on some large earthmoving tyres being operated in rocky conditions where the sidewalls of the tyres are susceptible to abrasion and cutting. The sidewall protectors are usually made of rubber and are contoured to conform to the bulge in the sidewall of the tyres. Mounting holes are commonly provided at the radially inner periphery for fastening the sidewall protectors to the rim on which the tyre is mounted.
One problem associated with such sidewall protectors is that of how to build them economically on a production basis with a high degree of uniformity. Although several existing techniques currently used for building a tyre carcass with strips of extruded rubber can be utilized in the building operation, the completely different structure poses problems not encountered in the building of tyres. For example, the sidewall protectors have a plurality of mounting holes at their radially inner periphery. Additionally some sidewall protectors have a pair of side ribs concentric with and adjacent their inner periphery. Since tyres do not have comparable mounting holes or the equivalent of the ribs, new apparatus and procedures are required for forming such holes and ribs.
In one aspect of the present invention, an apparatus for use in forming a mounting portion of an annular elastomeric article, particularly a tyre sidewall protector, comprises a mould having a first surface for moulding one side facing surface of the annular article; a plate having one side facing the mould first surface for moulding a portion of the other side facing surface of the annular article; a plurality of punches connected to the plate and_:extending from the one side of the plate; means for defining a central opening in the annular article; and means for moving the plate toward the mould to cause the punches to pierce the annular article.
- In another aspect of the present invention, a method of forming a mounting portion of an annular elastomeric article includes the steps of providing uncured elastomer on the mould of such an apparatus to form the annular article; moving the plate towards the mould; piercing the uncured annular elastomeric article with the punches on the plate and forming a plurality of holes in the annular article; and connecting the plate to the mould with at least a portion of the annular article sandwiched therebetween.
The method may further comprise the steps of placing the mould, annular article and plate in a _, vulcanizing apparatus; and curing the annular elastomeric article.
This apparatus and method solve the problem of how to build sidewall protectors and form the mounting portion thereof on a production basis with a high degree of uniformity, by providing a mould, on which the basic sidewall protector is formed, and a separate plate for forming the mounting portion of the sidewall protector while it remains on the mould. Since uncured rubber has a high resistance to flow, the plate may be resiliently biassed toward the mould so that movement of the plate to the final finish position takes place during the curing process wherein the rubber is heated to a vulcanizing temperature at which rubber flows more easily.
An example of the apparatus and method in accordance with the present invention will now be described with reference to the accompanying drawings, in which:-

Figure 1 is a partial side elevation;
Figure 2 is an enlarged view of a portion of the apparatus shown in Figure 1;
Figure 3 is an enlarged section taken on the line III-III in Figure 1,' also showing a linear actuator; and,
Figure 4 shows a part of the apparatus of Figure 3 but with certain elements in another position.

Referring now to Figures 1 and 3 of the drawings, an apparatus for forming mounting holes 10 and a central opening 11 in an annular elastomeric article, for example a tyre sidewall protector 12, is generally indicated by the reference numeral 13. The apparatus also forms a pair of annular ribs 14, 16 extending laterally outwardly from side surfaces 17, 18 of the article 12 and concentric with the central opening 11.
The apparatus 13 includes a rigid mould 19 having first and second mould portions 21, 22 connected in a back to back relationship by suitable structural members. Since the first and second mould portions are structurally identical only the first mould portion 21 will be described in detail with common reference numerals applied to counterpart elements of the second mould portion 22.
As more clearly shown in Figure 3 the first mould portion 21 has a surface 23 matching the side surface 17 of the sidewall protector 12. The first mould portion has a central opening 24 and a pair of concentric grooves 26, 27 in the surface 23 concentric with the central opening 24. A plurality of holes, one shown at 28, extend through the first mould portion and. are arranged in a pattern concentric with the central opening 24.
First and second plate assemblies 29,31 are releasably connectable to the first and second mold portions 21,22 respectively. The first plate assembly 29 is shown in Fig. 3 connected to the first mold portion 21 at a position at which the mounting holes 10 are partially formed as will be hereinafter described. The second plate assembly 31 is shown in Fig. 3 loosely connected to the second mold portion 22 prior to its being moved to the position illustrated by the first plate assembly 29 in Fig. 3. In Fig. 4 the first plate assembly 29 is'shown connected to the first mold portion 21 and at a position which it will occupy after the sidewall protector 12 is vulcanized as will be hereinafter described.
Since the first and second plate assemblies 29,31 are structurally identical only the first plate assembly 29 will be.described with comparable reference numerals applied to counterpart elements of the second plate assembly 31. The first plate assembly 29 includes an annular plate 32 having opposite sides 33,34. The side 33 is shaped to match a portion of the other side surface 18 of the sidewall protector 12 and has an annular groove 36 formed therein to form the annular rib 16. A plurality of tubular punches 37 are seated in holes 38 and extend axially outwardly from the side 33. The punches 37 are arranged in a predetermined pattern matching the pattern of the mounting holes 10 ' in the sidewall protector 12. An annular ring 39 is connected to and extends axially outwardly from the side 33 of the annular plate 32 and provides a means for forming the central opening 11 in the sidewall protector 12. At the position shown in Fig. 4 the distal end of the annular ring 39 extends into the groove 27 which acts as a pilot for precisely aligning the plate 32 relative to the first mold portion 21. A plurality of holes 41 extend through the plate 32 and are positioned in axial alignment with the holes 28 in the first mold portion 21.
A means 42 is provided for moving the first plate assembly 29 toward the first mold portion 21. The means 42 can include, for example, means 44 for resiliently biasing the plate 32 toward the first mold portion 21 in response to being compressed by a linear actuator 43. The resilient biasing means 44 can include a plurality of pins 46 individually slidably extendable through the holes 28,41, a plurality of springs 47 each encircling one of the pins 46 and positioned between the annular plate 32 and an enlarged head portion 48 at an end 49 of the respective pin, and a means 51 for connecting.an opposite end 52 of each pin to the first mold portion 21. The means 51 can include, for example, a hole 53 extending transversely through each pin 46 and a dowel 54 slidably insertable into the hole 53. Each of a plurality of cages ⁵⁶ surrounds a respective spring 47 and is connected to the annular plate 32 by bolts 57 (Figure 2).
As more clearly shown in Figs. 2 and 3, a pair of L-shaped members 61 are connected to the side 33 of plate 32 (only the member connected to plate 32 of plate assembly 31 is shown). Each member 61 has an arm 62 extendable through the central opening 24 of the first mold portion 21. A lock 63^- is positioned within a slot 64 in the respective arm 62 and is pivotally connected to the arm by a pin 66. A stop surface 67 is formed on the lock 63 and is engageable with a stop surface 68, which forms the back surface of the slot 64, for temporarily holding the plate 32 relative to the respective mold portion and for preventing inadvertent separation of the plate 32 from the respective mold portion 21,22 during the process of disconnecting the plate 32 from the respective mold portion.
The linear actuator 43 is mounted on a frame 71 and has an adapter head 72 connected to a piston rod 73. A pair of rollers, one partially shown at 74, are connected to the frame. Pressurized fluid can be selectively delivered to the actuator 43 through a line 76 from a source of pressurized fluid, not shown, in the usual manner.
In the use of the apparatus 13, with the first.and second plate assemblies 29,31 removed from the mold 19 a pair of the sidewall protectors 12 are laid up in the respective first and second mold portions 21,22 from extruded strips of uncured rubber while the mold is being rotated about its central axis in a suitable rotating device. Preferably, the inner portions of the sidewall protectors are built slightly oversize to provide an excess of rubber for flowing rubber into the grooves 26,36 to form the annular ribs 14,16 during curing.
One of the plate assemblies 29,31 is then loosely connected to the respective mold portion 21,22 with the pins 46 being in axial alignment with holes 28 in the mold portion. The frame 71 carrying the linear actuator 43 is then positioned with the rollers 74 in engagement with the backside of the respective mold portion 21,22 and the adaptor head 72 in engagement with the end 49 of the pin 46. Pressurized fluid is then delivered to the linear actuator 43 through the line 76 causing the piston rod 73 to extend. Extension of the piston rod 73 moves the pin 46 inwardly compressing the spring 47 which biases the plate 32 toward the mold portion and causes the adjacent punches 37 to partially pierce the uncured rubber making up the sidewall protector 12. The degree of penetration by the punches 37 will be limited and will depend on the compression of the spring 47 and the resistance to flow of the uncured rubber. The dowel 54 is inserted into the hole 53 in the pin 46 when the hole 53 becomes visible at the backside of the mold portion. The fluid pressure in the linear actuator 43 is then released leaving the pin 46 in the position shown in Fig. 3 wherein the spring 47 is exerting a biasing force against the plate 32 urging it toward the mold portion.
The frame 71 and hence the linear actuator 43 is then moved to the other pins 46 in any desirable sequence and the above process repeated until all the pins 46 are connected to the mold portion and all of the springs 47 compressed. The plate 32 of the other plate assembly 29,31 is then connected to the other mold portion 21,22 and the above process repeated.
When both plate assemblies 29,31 are connected to the respective first and second mold portions 21,22 the apparatus 13 is then positioned within a vulcanizing chamber such as an autoclave. Steam is then circulated through the vulcanizing chamber heating the uncured rubber forming the sidewall protectors to a curing temperature. As the temperature of the rubber increases its resistance to flow decreases so that the springs 47 urge the plates 32 toward the respective first and second mold portions 21,22 thereby completing the piercing of the holes 10. Simultaneously the inner portion of the sidewall protector between the plate 32 and the respective mold portion 21,22 is squeeezed causing the uncured rubber to flow into the grooves 26,36 forming the annular ribs 14,16. Also the annular ring 39 enters the groove 27 so that the central opening 11 of the sidewall protector 12 is accurately formed. Engagement of the punches 37 with the respective mold portion serves as a stop for controlling the thickness of the mounting portion of the sidewall protector.
After the sidewall protectors 12 are cured the apparatus 13 is removed from the vulcanizing chamber. The linear actuators 43 are again utilized to compress the springs 47 so that each dowel 54 can be removed from the associated hole 53, thereby uncoupling the pin 46 from the respective mould portion 21. With the lock 63 rotated clockwise 90° from the position shown in Figure 3 the plate assemblies 29,31 are then removed and the cured sidewall protectors 12 stripped from the first and second mould portions 21, 22.
Although the apparatus 13 is described as having first and second mould portions 21,22 and first and second plate assemblies 29, 31, in some cases the apparatus can be provided with only one mould portion and one plate assembly. Also, the moving means 42 could be a heavy duty press capable of physically forcing the punches 37 completely through the uncured rubber and causing the uncured rubber to flow into the grooves 26, 36 to form the annular ribs 14, 16 prior to the step of vulcanizing the sidewall protectors.
In._'view of the foregoing it is readily apparent that an improved method and apparatus is provided for. building sidewall protectors and for forming the mounting portion thereof on a production basis with a high degree of uniformity. This is accomplished by providing a mould in which the sidewall protector can be laid up with automated equipmentand providing a separate device for forming the mounting portion of the sidewall protector while it remains in the mould. , Furthermore, by resiliently biasing the plate assembly toward the mould so that the final forming of the mounting portion takes place during the curing step, a relatively light weight actuator can be used thereby negating the need for a large and expensive heavy-duty press for moving the plate assembly toward the mould.

Claims

1. Apparatus (13) for use in forming the mounting portion of an annular elastomeric article (12), particularly a tyre sidewall protector, the apparatus comprising a mould (19) having a first surface (23) for moulding one side facing surface (17) of the annular article; a plate (32) having one side (33) facing the mould first surface (23) for moulding a portion of the other side facing surface (18) of the annular article; a plurality of punches (37) connected to the plate (32) and extending from the one side (33) of the plate; means (39) for defining a central opening (11) in the annular article (12); and means (42) for moving the plate (32) toward the mould (19) to cause the punches (37) to pierce the annular article (12).

2. Apparatus according to claim 1, wherein the moving means (42) comprises means (44) for resiliently biasing the plate (32) towards the mould (19).

3. Apparatus according to claim 2, wherein the apparatus further comprises a plurality of holes (28) in the mould (19), an equal number of holes (41) being provided in the plate (32) in axial alignment with the holes (28) in the mould; and wherein the resilient biasing means comprises a plurality of pins (46) individually slidably extending through respective pairs of holes (28, 41) in the plate (32) and the mould (19), each of the pins having an enlarged head portion (48) at one end,and means (51) for releasably connecting the other end of the pin (46) to the mould; and a compression spring (47) positioned between the enlarged head portion (48) of the pin (46) and the plate (32).

4. Apparatus according to claim 3, further comprising a plurality of cages (56) connected to the plate (32), each of tho cages (56) surrounding a respective one of the springs (47).

5. Apparatus according to claim 3 or claim 4, further comprising a linear actuator (43) engageable with the mould and having a movable member (72,73) adapted for engagement with the one end (49) of one of the pins (46) for compressing the spring (47) associated with the one pin (46).

6. Apparatus accordirgto any of the preceding claims, wherein the means (39) for defining the central opening comprises an annular ring (39) mounted on the one side (33) of the plate (32).

7. Apparatus according to claim 6, further comprising an annular groove (27) in the first surface (23) of the mould (19), the groove being positioned to receive the annular ring (39), in use. -

8. Apparatus according to any of the preceding claims, further comprising a first annular groove (26) in the first surface (23) of the mould (19), and a second annular groove (36) in the one side (33) of the plate (32).

9. Apparatus according to any of the preceding claims for use in forming the mounting portions of two annular elastomeric articles, wherein the mould (19) has a second surface (23) for moulding one side facing surface (17) of another annular article (12), the second surface (23) facing away from the first surface; the apparatus further comprising another plate (32) having one side (33) facing the second mould surface (23) for moulding a portion of the other side facing surface (18) of the another annular article, and another plurality of punches (37) connected to the another plate (32) and extending from the one side (33) of the another plate (32).

10. A method of forming a mounting portion of an annular elastomeric article (12), the method including the steps of providing uncured elastomeric material on the mould (19) of an apparatus (13) according to any of the preceding claims to form the annular article; moving the plate (32) towards the mould;-piercing the uncured annular elastomeric article with the punches (37) on the plate and forming a plurality of holes (10) in the annular article; and connecting the plate (32) to the mould with at least a portion of the annular article (12) sandwiched therebetween.

11. A method according to claim 10, further comprising the steps of placing the mould, annular article (12) and plate (32) in a vulcanizing apparatus; and curing the annular elastomeric article.

12. A method according to claim 11, characterized in that the plate (32) is resiliently biased towards the mould during the curing step.

13. A method according to any of claims 10 to 12, when dependant on claim 3, further comprising the steps of compressing the plurality of springs (47), and connecting the other end of each pin (46) to the mould (19). ,